Design of Mold Materials for Encapsulating Semiconductors Using Epoxy Molding Compounds

Mold materials have been found which have excellent releasabilities. This was achieved by inhibiting mold adhesion caused by acid-base interactions between epoxy molding compounds (EMCs) used for encapsulating semiconductors and hydroxyl groups on the mold surface. Some rare-earth oxides, which have isoelectric points of the surface (IEPS) in the range 9 to 10, have excellent releasability from EMCs. In particular, the releasing force of Y 2 O 3 is 10 times smaller than that of conventional mold materials for alloy tool steels. It has thus received considerable attention for use as a mold material. It was found that the releasability depends on the arithmetic difference between the IEPS of the mold material and the dissociation constant of the EMC species.